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imc

geometry intermediate

Problem

The diagram shows lattice points, each one unit from its nearest neighbors. Segment meets segment at . Find the length of segment .
problem
(A)
(B)
(C)
(D)
Solution
Let be the line containing and and let be the line containing and . If we set the bottom left point at , then , , , and . The line is given by the equation . The -intercept is , so . We are given two points on , hence we can compute the slope, to be , so is the line Similarly, is given by . The slope in this case is , so . Plugging in the point gives us , so is the line . At , the intersection point, both of the equations must be true, so We have the coordinates of and , so we can use the distance formula here: which is answer choice
Final answer
B